This invention relates generally to precast concrete and insulation composite panels in which a layer of insulation is sandwiched between exterior layers of concrete.
Referring to FIG. 6, a known concrete and insulation composite panel 20 is composed of two layers or wythes of concrete 22, 24 separated by a layer of high density foam insulation 26 in the center. The thickness of the concrete wythes varies depending upon the structural requirements of the building. The most common load requirements include wind load, roof load, and seismic load. These loads must be collected and then transferred to the building frame and the building foundation. The two concrete wythes 22, 24 handle the majority of this work in concert. But, when the concrete wythes 22, 24 are separated by an insulation layer 26, one or more structural tie shear connectors 28 are used to connect the two concrete wythes together across the insulation layer in such a manner as to cause the two concrete wythes to function more as a single composite unit structurally. Such connectors 28 transfer load forces, for example, wind forces, imposed on one concrete wythe 22 across the insulation layer 26 and into the other concrete wythe 24. With the structural tie shear connector, the two concrete wythes act in concert to provide a singular load-resisting element greater than the sum capacities of the individual concrete layers. A concrete and insulation panel of the type described above is further shown and described in U.S. Pat. No. 6,088,985.
While such a connector 28 provides satisfactory performance, it is desirable that its performance be improved. For example, during the manufacturing process, an initial bond is created between the concrete wythes 22, 24 and insulation layer 26, but this bond is eventually broken due to handling, thermal differentials and cycling, or service loads. Therefore, the structural tie shear connectors 28 are solely responsible for maintaining the structural integrity of the panel 20. For example, the shear connectors 28 are effective to transfer forces between the wythes 22, 24 due to longitudinal bending of a panel. The shear connectors 28 have sufficient strength and stiffness to allow a significant level of interaction between the concrete wythes 22, 24 in the resistance of normally expected loads. However, if the panel 20 is subjected to greater loads, it is possible for ends 36, 38 of the connector 28 to pivot slightly with respect to a connection point 40 in the plane of the connector 28. Any such motion or any other relative motion between different portions of the connector 28, allows small but discrete independent motions of the concrete wythes 22, 24. That independent motion of the concrete wythes 22, 24 can reduce the structural integrity of the composite panel 20. Thus, there is a need for a structural tie shear connector that is stiffer and stronger.
In another example, referring to FIG. 6, the connector 28 has a pair of anchors 30 that facilitate locating the connector 28 in the concrete wythe 24 during the manufacture of the concrete and insulation composite panel 20. The nominal size of the connector 28 is related to the nominal thickness of the panel as measured across the concrete wythes 22, 24 and the insulation 26. When a panel 20 is to be used in the construction of a building, it can be made in different nominal sizes, for example, 6 inches, 8 inches, 10 inches, 12 inches, etc. Thus, a different connector 28 must be made for each different thickness of the panel 20. Such a requirement generally increases costs from the manufacturer to the end user of the connector 28. Therefore, there is a need for a single structural tie shear connector that can be used with concrete and insulation composite panels of different sizes or thicknesses.
The present invention provides a structural tie shear connector that is stronger, more rigid, more reliable and has greater application flexibility than known connectors. The structural tie shear connector of the present invention permits a concrete and insulation composite panel to reliably react greater load forces without distortion, thereby improving the structural integrity of the panel. Further, the structural tie shear connector of the present invention can be used with concrete and insulation composite panels of different thicknesses; and thus, the connector has greater application flexibility and provides for reduced manufacturing and inventory costs.
According to the principles of the present invention and in accordance with the described embodiments, the invention provides a structural tie shear connector for use with a concrete and insulation composite panel. The panel has a first concrete wythe, a second concrete wythe, and an insulation layer interposed between the first and second concrete wythes. The connector has two sides extending in a direction substantially parallel to a longitudinal centerline of the connector and two sides extending across the longitudinal centerline of the connector. First and second pairs of angular links are connected to the sides, and a pair of legs are connected to, and extend outward from, one side of the connector. The connector is extendable through the insulation layer and into the first and second concrete wythes to hold the panel together. The two sides that cross the longitudinal centerline extend across a substantial width of the connector and function to stiffen and strengthen the connector.
In one aspect of this invention, the connector has another pair of legs that are connected to, and extend outwardly from, another side of the connector immediately adjacent the one side. The second pair of legs are also extendable into a concrete wythe. The connector has a substantially rectangular shape; and therefore, the two pairs of legs can be used with composite panels having different thicknesses.
In another embodiment, the invention provides a concrete and insulation composite panel having two concrete wythes with a layer of insulation interposed therebetween. The insulation layer has two insulation strips disposed side-by-side between the two concrete wythes to form a gap between the two insulation strips. Flexible foam is disposed in the gap between the two insulation strips. A structural tie shear connector is disposed in the gap against the flexible foam and extends into the first and second concrete wythes to hold the panel together. The flexible foam helps secure the structural tie shear connector in its desired location while the concrete wythes are being poured and cured; and in addition, the flexible foam fills the gap, so that the gap cannot be bridged by wet concrete.
These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein.